this idea probably has no real benefit, but its late and im just thinking about this
you could put a small check valve on the vent tube and pressurize the tank with a couple pounds of pressure before say a drag race to have added pressure???
not sure what it would do but just a thought
Increasing the tank pressure will increase the flow. 1 psi of pressure at the float valve will approximately double the fuel flow over what you would have with a gravity feed system when the fuel tank is full. A fuel level in the gas tank that is 1 foot above the the float valve will produce approximately 0.4 to 0.5 psi at the float valve.
The float valves on the majority of the PJ or PWK type of Keihin carburetor are sized for gravity feed. Float valves sized for gravity feed will stop holding as the pressure approaches 1 psi. When the float valve stops holding, the fuel level will rise causing an extreme rich condition in addition to fuel overflowing out of the vent lines. The float valve seat on the Keihin carbs cannot be replaced with different sizes like the Mikuni carbs. Mikuni offers this feature of replaceable seat sizes to accommodate a wide range of fuel pressures to the carb.
Sizing the seat size with the correct fuel pressure to get maximum flow sometimes takes a lot of testing to find the right combination. I often use variable fuel pressure systems to offer low pressure when the fuel demand is low and higher pressure at higher fuel demands on the methanol systems.
